Mumps Outbreak Hits New York, New Jersey

Feb. 11, 2010 - An ongoing mumps outbreak has sickened 1,521 people in New York and New Jersey.

"Patient Zero" was an 11-year-old boy who got infected with mumps during a summer visit to Great Britain. He came down with symptoms while at a summer camp for Orthodox Jewish boys; campers and staff then carried the disease back to their communities.

The infections happened despite high coverage with the measles-mumps-rubella (MMR) vaccine. Among patients ages 7 to 18 -- the age group that had the most cases -- 85% of patients had received the two recommended MMR vaccine doses.

"Two doses of mumps vaccine is believed to be 90% to 95% effective," Gallagher tells WebMD. "But that means people can still get mumps. If the vaccine is 90% effective and 100 people are exposed to mumps, 10 will get the disease."

In the U.K., the source of the outbreak, MMR vaccination rates remain low due to fears that the vaccine might be linked to autism. The small, 12-year-old study that spurred those fears has been retracted by the journal that published it and disavowed by 10 of its 13 authors. The doctors who did not disavow the study have been rebuked by U.K. authorities and face revocation of their medical licenses.

The U.S. mumps outbreak is the worst since an 11-state outbreak sickened 2,597 people from December 2005 to May 2006.

Over three-fourths of the cases have been in males, as the outbreak is spreading mostly in Orthodox Jewish schools for boys. Fewer than 3% of the cases have occurred outside Orthodox Jewish communities, mostly in people with close community contact.